The History of Middle-earth (chibi version) - Part 209 - To arms!

We know that there have been orcs wandering around Middle-earth for a while, having escaped the destruction of Utumno; they're why the Laiquendi headed to Beleriand, for instance. But I assume that until Morgoth's return to organise them they mostly avoided Thingol's kingdom; so while experienced and well-travelled warriors like Mablung might know what they are, more sheltered Sindar have never heard of them until now.